Can Alterations in Cerebrovascular CO<sub>2</sub> Reactivity Be Identified Using Transfer Function Analysis without the Requirement for Carbon Dioxide Inhalation?
The present study aimed to examine the validity of a novel method to assess cerebrovascular carbon dioxide (CO<sub>2</sub>) reactivity (CVR) that does not require a CO<sub>2</sub> inhalation challenge, e.g., for use in patients with respiratory disease or the elderly, etc. In...
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MDPI AG
2023-03-01
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| Series: | Journal of Clinical Medicine |
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| Online Access: | https://www.mdpi.com/2077-0383/12/6/2441 |
| _version_ | 1797610931694338048 |
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| author | Shigehiko Ogoh Hironori Watanabe Shotaro Saito James P. Fisher Erika Iwamoto |
| author_facet | Shigehiko Ogoh Hironori Watanabe Shotaro Saito James P. Fisher Erika Iwamoto |
| author_sort | Shigehiko Ogoh |
| collection | DOAJ |
| description | The present study aimed to examine the validity of a novel method to assess cerebrovascular carbon dioxide (CO<sub>2</sub>) reactivity (CVR) that does not require a CO<sub>2</sub> inhalation challenge, e.g., for use in patients with respiratory disease or the elderly, etc. In twenty-one healthy participants, CVR responses to orthostatic stress (50° head-up tilt, HUT) were assessed using two methods: (1) the traditional CO<sub>2</sub> inhalation method, and (2) transfer function analysis (TFA) between middle cerebral artery blood velocity (MCA V) and predicted arterial partial pressure of CO<sub>2</sub> (PaCO<sub>2</sub>) during spontaneous respiration. During HUT, MCA V steady-state (i.e., magnitude) and MCA V onset (i.e., time constant) responses to CO<sub>2</sub> inhalation were decreased (<i>p</i> < 0.001) and increased (<i>p</i> = 0.001), respectively, indicative of attenuated CVR. In contrast, TFA gain in the very low-frequency range (VLF, 0.005–0.024 Hz) was unchanged, while the TFA phase in the VLF approached zero during HUT (−0.38 ± 0.59 vs. 0.31 ± 0.78 radians, supine vs. HUT; <i>p</i> = 0.003), indicative of a shorter time (i.e., improved) response of CVR. These findings indicate that CVR metrics determined by TFA without a CO<sub>2</sub> inhalation do not track HUT-evoked reductions in CVR identified using CO<sub>2</sub> inhalation, suggesting that enhanced cerebral blood flow response to a change in CO<sub>2</sub> using CO<sub>2</sub> inhalation is necessary to assess CVR adequately. |
| first_indexed | 2024-03-11T06:21:51Z |
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| institution | Directory Open Access Journal |
| issn | 2077-0383 |
| language | English |
| last_indexed | 2024-03-11T06:21:51Z |
| publishDate | 2023-03-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Journal of Clinical Medicine |
| spelling | doaj.art-26023aa589da490483425b9ab0839f4a2023-11-17T11:52:55ZengMDPI AGJournal of Clinical Medicine2077-03832023-03-01126244110.3390/jcm12062441Can Alterations in Cerebrovascular CO<sub>2</sub> Reactivity Be Identified Using Transfer Function Analysis without the Requirement for Carbon Dioxide Inhalation?Shigehiko Ogoh0Hironori Watanabe1Shotaro Saito2James P. Fisher3Erika Iwamoto4Department of Biomedical Engineering, Toyo University, Kawagoe 350-8585, JapanDepartment of Biomedical Engineering, Toyo University, Kawagoe 350-8585, JapanDepartment of Biomedical Engineering, Toyo University, Kawagoe 350-8585, JapanDepartment of Physiology, Faculty of Medical and Health Sciences, University of Auckland, Auckland 1023, New ZealandSchool of Health Sciences, Sapporo Medical University, Sapporo 060-8556, JapanThe present study aimed to examine the validity of a novel method to assess cerebrovascular carbon dioxide (CO<sub>2</sub>) reactivity (CVR) that does not require a CO<sub>2</sub> inhalation challenge, e.g., for use in patients with respiratory disease or the elderly, etc. In twenty-one healthy participants, CVR responses to orthostatic stress (50° head-up tilt, HUT) were assessed using two methods: (1) the traditional CO<sub>2</sub> inhalation method, and (2) transfer function analysis (TFA) between middle cerebral artery blood velocity (MCA V) and predicted arterial partial pressure of CO<sub>2</sub> (PaCO<sub>2</sub>) during spontaneous respiration. During HUT, MCA V steady-state (i.e., magnitude) and MCA V onset (i.e., time constant) responses to CO<sub>2</sub> inhalation were decreased (<i>p</i> < 0.001) and increased (<i>p</i> = 0.001), respectively, indicative of attenuated CVR. In contrast, TFA gain in the very low-frequency range (VLF, 0.005–0.024 Hz) was unchanged, while the TFA phase in the VLF approached zero during HUT (−0.38 ± 0.59 vs. 0.31 ± 0.78 radians, supine vs. HUT; <i>p</i> = 0.003), indicative of a shorter time (i.e., improved) response of CVR. These findings indicate that CVR metrics determined by TFA without a CO<sub>2</sub> inhalation do not track HUT-evoked reductions in CVR identified using CO<sub>2</sub> inhalation, suggesting that enhanced cerebral blood flow response to a change in CO<sub>2</sub> using CO<sub>2</sub> inhalation is necessary to assess CVR adequately.https://www.mdpi.com/2077-0383/12/6/2441CO<sub>2</sub> inhalationtime responsemagnitude responsetransfer function analysisbrain blood flow |
| spellingShingle | Shigehiko Ogoh Hironori Watanabe Shotaro Saito James P. Fisher Erika Iwamoto Can Alterations in Cerebrovascular CO<sub>2</sub> Reactivity Be Identified Using Transfer Function Analysis without the Requirement for Carbon Dioxide Inhalation? Journal of Clinical Medicine CO<sub>2</sub> inhalation time response magnitude response transfer function analysis brain blood flow |
| title | Can Alterations in Cerebrovascular CO<sub>2</sub> Reactivity Be Identified Using Transfer Function Analysis without the Requirement for Carbon Dioxide Inhalation? |
| title_full | Can Alterations in Cerebrovascular CO<sub>2</sub> Reactivity Be Identified Using Transfer Function Analysis without the Requirement for Carbon Dioxide Inhalation? |
| title_fullStr | Can Alterations in Cerebrovascular CO<sub>2</sub> Reactivity Be Identified Using Transfer Function Analysis without the Requirement for Carbon Dioxide Inhalation? |
| title_full_unstemmed | Can Alterations in Cerebrovascular CO<sub>2</sub> Reactivity Be Identified Using Transfer Function Analysis without the Requirement for Carbon Dioxide Inhalation? |
| title_short | Can Alterations in Cerebrovascular CO<sub>2</sub> Reactivity Be Identified Using Transfer Function Analysis without the Requirement for Carbon Dioxide Inhalation? |
| title_sort | can alterations in cerebrovascular co sub 2 sub reactivity be identified using transfer function analysis without the requirement for carbon dioxide inhalation |
| topic | CO<sub>2</sub> inhalation time response magnitude response transfer function analysis brain blood flow |
| url | https://www.mdpi.com/2077-0383/12/6/2441 |
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